Rotary hydraulic machines of the subject type generally include a housing, a rotor mounted for rotation with in the housing and having a plurality of radially extending peripheral slots, and a plurality of vanes individually slidably mounted in the slots. A cam ring surrounds the rotor and has a radially inwardly directed surface forming a vane track and one or more fluid pressure cavities between the cam surface and the rotor. Inlet and outlet passages feed hydraulic fluid to and from the cavities.
It is necessary in operation of machines of this character that the rotor vanes slidably engage the opposing cam ring surface. During operation, the vanes are urged outwardly against the cam ring surface by centrifugal force. However, there are many conditions existing and forces created tending to prevent the vanes from acting freely as cam ring surface followers, and also causing the vanes to collapse or retract from the vane track, such as both mechanical and viscous friction, bearing loads of the vanes against the track or between the vane and rotor, and differential pressures creating unfavorable resultant forces acting on the extreme inner or outer edges of the vanes. Further, upon initial operation of the machine, it is undesirable to permit the vanes to be spaced from the opposing cam ring surface, both because of pressure loss as fluid freely flows over the vanes, and also because centrifugal forces can cause the vanes to be damaged by impact against the cam ring surface.
To overcome the aforementioned problems, it has heretofore been proposed to form chambers in the rotor beneath the vane slots. Springs are positioned within these rotor chambers and/or fluid is fed under pressure to the rotor chambers for urging the vanes radially outwardly against the cam ring surface. The vane springs, where employed, exhibit varying spring rate both among individual springs and over the operating life of a given spring, possess a limited operating life, and frictionally wear against the opposing edges of the vanes. Provision of undervane fluid pressure, either intermittent or continuous, usually requires the use of valves for feeding the fluid to the undervane chambers prior to the primary machine cavities, and also does not overcome the problem of vane impact against the cam ring surface except where combined with the vane springs. So-called inner vane machines have addressed but not entirely overcome the problems in question.
One object of the present invention, therefore, is to provide a rotary hydraulic machine of the subject character that includes facility ensuring that the vanes are continually positioned adjacent to the cam ring surface, while overcoming the aforementioned deficiencies in the art. Another and related object of the invention is to provide a rotary hydraulic machine of the described character that overcomes the aforementioned deficiencies in the art, that continually positions the vanes adjacent to the cam ring surface while reducing frictional wear, and that is less expensive to manufacturer than are prior art machines of similar type.
Another problem addressed by the present invention lies in the provision of hydraulic apparatus for dividing a single input flow of hydraulic fluid into two or more output flows at a predetermined flow ratio. Prior art devices for this purpose have involved relatively complex and expensive specialized structures. Yet another object of the present invention, therefore, is to provide a hydraulic fluid flow divider that is inexpensive to manufacture and assemble, and that is reliable over an extended operating lifetime.